Applying NEC to 46kV substation designed to NESC

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
Hi everyone, I could use some help.
1. Is it possible to review a 46kV substation under the NEC but the substation was designed to meet NESC?
2. Why or why not? Are there safety hazards created?

This is a real situation. A PV facility is constructing a substation for a local utility, however, since the substation is not being constructed directly by the utility, the code exemption to the NEC is not applicable. A building permit needs to be submitted and the substation will need to meet the NEC.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
I would say 490.98 would be a great place to start.
It says a PE will design the fence. It’s on the PE IMO.

One example, 250.198 says fence to be grounded IF within 16’ of energized parts.
NESC says all fences will be effectively grounded.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The NEC does a very poor job with medium voltage systems. I would permit and inspect to the NESC as that document has the expertise in this area...the NEC does not. In many cases the local AHJ will bring in an engineer experienced in medium voltage systems for the plan review and the inspection.

There is a to start bringing more medium voltage stuff into the NEC for this very reason. It appears this process will start with the 2023 code by moving the few existing medium voltage rules into their own articles. The intent is that additional rules will be added in the 2026 and future code cycles because there is more and more privately owned medium voltage systems being installed.
 
Last edited:

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
The NEC does a very poor job with medium voltage systems. I would permit and inspect to the NESC as that document has the expertise in this area...the NEC does not. In many cases the local AHJ will bring in an engineer experienced in medium voltage systems for the plan review and the inspection.

There is a more to start bringing more medium voltage stuff into the NEC for this very reason. It appears this process will start with the 2023 code by moving the few existing medium voltage rules into their own articles. The intent is that additional rules will be added in the 2026 and future code cycles because there is more and more privately owned medium voltage systems being installed.
City electrical code is only to the NEC. Staff is not familiar with medium voltage installations. Reviewing the 45kV substation to NEC is a bad idea. I need to be able to explain why.

1. I don't think the substation can be completely reviewed by NEC, certain components and configuration cannot be adressed at 46kV, i.e. Bus, transmission line, transformer.

2. One safety concern. Substations are designed to be worked on when live, forcing the substation design to fit NEC may increase risk of those that maintain facility.

I'm trying to prevent a public safety issue and uncessary liability for the City. But I'm not sure if applying the NEC to a substation rises to that level of concern.

Thanks again for help.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
City electrical code is only to the NEC. Staff is not familiar with medium voltage installations. Reviewing the 45kV substation to NEC is a bad idea. I need to be able to explain why.

1. I don't think the substation can be completely reviewed by NEC, certain components and configuration cannot be adressed at 46kV, i.e. Bus, transmission line, transformer.

2. One safety concern. Substations are designed to be worked on when live, forcing the substation design to fit NEC may increase risk of those that maintain facility.

I'm trying to prevent a public safety issue and uncessary liability for the City. But I'm not sure if applying the NEC to a substation rises to that level of concern.

Thanks again for help.
Sorry about my post above. I just noticed it reads like crap.
490.98 says an engineer will design the substation.
It’s on the PE.

Design it to NESC, and stamp it. That satisfies 490.98 IMO
 

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
Sorry about my post above. I just noticed it reads like crap.
490.98 says an engineer will design the substation.
It’s on the PE.

Design it to NESC, and stamp it. That satisfies 490.98 IMO
The comment about the fence was helpful. The problem is, the city is forcing a review under the NEC. The NESC is not an option, the city only regulates NEC, not NESC. The substation is not eligible for the NEC exemption written into local code because it is not being constructed by a utility provider. I don't think this substation can be reviewed under the NEC because that's not what the NEC is designed to do. The problem I'm running into, generally, engineers are either are knowledgeable on the NEC or NESC and not both. I can't get a straightforward answer even though it's common knowledge the NESC is more distrubtion provider side and NEC is user side. Now, the city is forcing NEC compliance, and I can't clearly explain why this is a terrible idea.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The comment about the fence was helpful. The problem is, the city is forcing a review under the NEC. The NESC is not an option, the city only regulates NEC, not NESC. The substation is not eligible for the NEC exemption written into local code because it is not being constructed by a utility provider. I don't think this substation can be reviewed under the NEC because that's not what the NEC is designed to do. The problem I'm running into, generally, engineers are either are knowledgeable on the NEC or NESC and not both. I can't get a straightforward answer even though it's common knowledge the NESC is more distrubtion provider side and NEC is user side. Now, the city is forcing NEC compliance, and I can't clearly explain why this is a terrible idea.
I don't think compliance with the NEC creates and hazards or safety issues, but compliance with just the NEC may miss hazards and safety issues that would not exist if the installation is in compliance with the NESC.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
The comment about the fence was helpful. The problem is, the city is forcing a review under the NEC. The NESC is not an option, the city only regulates NEC, not NESC. The substation is not eligible for the NEC exemption written into local code because it is not being constructed by a utility provider. I don't think this substation can be reviewed under the NEC because that's not what the NEC is designed to do. The problem I'm running into, generally, engineers are either are knowledgeable on the NEC or NESC and not both. I can't get a straightforward answer even though it's common knowledge the NESC is more distrubtion provider side and NEC is user side. Now, the city is forcing NEC compliance, and I can't clearly explain why this is a terrible idea.
What difference does it make what criteria the city is using to review the installation. You will still need to get knowledgeable people to design the thing. There are a lot of other places that have their own switchgear. This is not unique.

IMO, the city is not harming you by reviewing it by NEC standards. It is not the job of the city to determine if the design is suitable. That is the job of the P.E. that stamps the drawings.
 

Joe.B

Senior Member
Location
Arcata Ca
Occupation
Building Inspector
I hear you and I think you have good reason to be concerned, but I also think the answers given so far are all valid. If you're looking to NEC arguments to show your superiors why this system is "special" I would consider reading Article 90 and finding your reasoning there. Along with the above mentioned points as well. There are third party review companies who can provide plan review and inspection services.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
What difference does it make what criteria the city is using to review the installation. You will still need to get knowledgeable people to design the thing. There are a lot of other places that have their own switchgear. This is not unique.

IMO, the city is not harming you by reviewing it by NEC standards. It is not the job of the city to determine if the design is suitable. That is the job of the P.E. that stamps the drawings.

👍👍
That’s the exact point I’ve been trying to make.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
90.4 should cover the city legally for letting a PE stamp it to the NESC. Heck, the city could hire a NESC expert to inspect it. Just figure out if you can afford the fees.
 

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
What difference does it make what criteria the city is using to review the installation. You will still need to get knowledgeable people to design the thing. There are a lot of other places that have their own switchgear. This is not unique.

IMO, the city is not harming you by reviewing it by NEC standards. It is not the job of the city to determine if the design is suitable. That is the job of the P.E. that stamps the drawings.
It is the job of the city to determine it is safe, which code standard assures that, the NESC or NEC?
 

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
I really appreciate everyone’s input. I'm dealing with this from the City perspective. We can't stamp, approve, or review under the NESC, our electrical code is only to the NEC. Because of a gap in our code, we have staff reviewing Interconnection Facilities that have no experience reviewing high voltage facilities and they have to review under the NEC. My concern is safety, for that person that will need to maintain and repair the facilities, what is the safest code standard this facility needs to be reviewed under, it's clearly the NESC. It is the job of the PE to design the facility to NESC standards, and it is the job of the city to make sure it's correct, that is the only point of pulling a permit.
 

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
It sounds like the NEC could be used to address all the components of the 46kV substation; transmission line, bus, transformer, etc. Add staff do not have experience with reviewing substations, experience in only NEC, and electrical code is only to the NEC. City reviewing the facility for safety using NEC doesn't make sense and dangerous because substations are designed to the NESC, which have specific standards unique to the NESC to ensure safety.
 

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
I hear you and I think you have good reason to be concerned, but I also think the answers given so far are all valid. If you're looking to NEC arguments to show your superiors why this system is "special" I would consider reading Article 90 and finding your reasoning there. Along with the above mentioned points as well. There are third party review companies who can provide plan review and inspection services.
I wish there was more discussion about why utilities are exempt. A nice paragraph explaining the specific benefits to designing to NESC when compared to NEC. A Gap in our code is forcing the electric utility to comply with NEC.
 

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
I do get the facility can be designed to NESC and may be able to be reviewed under the NEC (still not sure if the NEC can comprehensivly review the electrical for a substation) and everything may be okay. My point, the city can't verify it meets the NESC and that we shouldn't even be reviewing these facilities for code compliance and safety, we don't have the qualifications or the right electrical code.
 

mrktaylor7

Member
Location
Hawaii
Occupation
Urban planner
The following document discusses some of the activity underway by the NFPA and IEEE to address the issues mentioned above. It is from 2017 but perhaps there are more recent updates available.

http://pubs.naruc.org/pub/6E6CF537-EC17-B314-BCB5-A6A610E273F2&usg=AOvVaw1vs7NK7kfJgJShUgoy3REe
The verbage is too specific in the NEC. Facilities under the direct control or own by public utility. My situation, the owners of the PV facility are building for the public utility. Not under the direct control or owned by the public utility yet. The power purchase agreement between the two parties stipulates the substation will be built to the public utilities standards before it is deeded over to the public utility. Exact same end product for the public utility facility, but different circumstances during construction. I got Corporation counsel involved and they made the determination the NEC exemption is not eligible. Thanks for link.
 
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